Today Twitter revealed that while it’s actually growing now—it added four million monthly Tweeters over the last three months—the company has made a crucial error: It accidentally inflated user growth in its reports for the previous three years.

On Thursday morning, Twitter released its quarterly earnings in a letter to shareholders. In the report, the company wrote that it recently discovered that, since the end of 2014, it had been erroneously counting users of apps that used Digits, Twitter’s now defunct developer toolkit, in its tally of monthly users.

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Twitter launched Digits in October of 2014. The service, released independently from the social network, was pitched to developers as a way for them to simplify how users signed up for (and logged into) their apps. But according to Twitter’s story, if you made an app and used Twitter’s Digits SDK over the past three years, the company might have counted your users as its own.

Twitter has since revised some of its numbers, shaving off a whopping 1 to 2 million active users per quarter since the end of 2016. But Twitter says it can’t adjust user numbers earlier than that, because it apparently doesn’t have the data to calculate how far off its reports may have been.

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When reached for comment, Twitter said it disclosed the issue in its shareholder letter and, in lieu of a comment, referred Gizmodo to the portion of the letter that addresses the mishap:

We discovered that since the fourth quarter of 2014 we had included users of certain third-party applications as Twitter MAUs that should not have been considered MAUs. These third-party applications used Digits, a software development kit of our now-divested Fabric platform, that allowed third-party applications to send authentication messages via SMS through our systems, which did not relate to activity on the Twitter platform.

Twitter declined a follow-up request from Gizmodo to make any further statements about the miscalculation.

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This new discovery means Twitter’s previously reported lack of growth was even more bleak that we thought. But Twitter did show today that its monthly active users grew by four percent in the last three months, hitting 330 million in the third quarter of this year. The company is also confident it may actually turn a profit for the first time ever in the fourth quarter. In light of the report, Twitter shares grew by more than 11 percent.